Seat

ABSTRACT

Described is a seat ( 10 ) comprising a seat squab ( 12 ) and a backrest ( 14 ) which is displaceable in respect of its inclination. In order to achieve a load relief for the intervertebral disc of a user of the seat and thus optimum seating comfort, the seat ( 10 ) provides that the backrest ( 14 ) is displaceable between convex lordosis positions and concave kyphosis positions in dependence on the respective backrest inclination.

The invention concerns a seat comprising a seat squab and a backrestwhich is adjustable in respect of its inclination.

Such a seat involves for example a vehicle seat for a land vehicle,aircraft or marine craft, or a chair such as an office chair or thelike.

Hitherto it was assumed that, when a person is sitting, the personshould adopt an upright position with a hollow back (lordosis). A largenumber of proposals have been put forward in that respect. By way ofexample WO 95/22307 describes a seat having a backrest, wherein lordosiscan be adjusted and displaced as desired.

A seat which is adjustable in respect of lordosis, in particular avehicle seat, is also known for example from DE 195 34 660 C1. Thatknown seat has a backrest with a number of pressure-actuable airchambers which are communicated with a control unit for controlling thepressure in the air chambers. The control unit is connected to anoperating unit which is actuable by a user of the seat in order toadjust the contour or the lordosis of the backrest of the seat, asdesired. With that known seat, the seat contour can be selectivelycurved forwardly in the upper, middle or lower portion of the lordosisregion, by way of expansion of a respectively corresponding air chamber,as is described at column 4, lines 31 through 34.

DE 41 16 836 A1 describes a vehicle seat having a mechanical massagedevice and EP 0 270 699 B1 discloses a vehicle seat with air chambersfor dynamic massage of the spinal column of a user of the seat, whereinthe backrest is adapted to the S-shaped curvature of the spinal columnof a user of the seat. This last-mentioned seat therefore also onlytakes account of lordosis.

Recent investigations however, on the basis of direct in-vivointervertebral disc pressure measurements, show that the ideas whichapplied hitherto of sitting upright with a hollow back can no longer besustained. In accordance with these most recent findings, sitting is nomore stressful than standing, in which respect when sitting the pressurein the intervertebral discs in the seated posture with a round back(=kyphosis), which hitherto was frowned upon as being casual and lax, iseven reduced to half. The comfortable seated posture with a slightlyround back produces a markedly lower level of pressure loading than theupright posture with a rounded back (=lordosis) which was hithertorecommended by the back experts.

In consideration of those aspects the object of the present invention isto provide a seat of the kind set forth in the opening part of thisspecification, with which it is not only possible to adopt a hollow-backposition but also a rounded-back position in order to correspondinglyrelieve the load on the intervertebral discs of the user of the seat.

In accordance with the invention, in a seat of the kind set forth in theopening part of this specification, that object is attained in that thebackrest is displaceable between convex lordosis positions and concavekyphosis positions in dependence on the respective backrest inclination.

The configuration according to the invention of the seat with a backrestwhich is displaceable between convex lordosis positions and concavekyphosis positions in dependence on the respective inclination of thebackrest affords the advantage that the spinal column of the respectiveuser of the seat can be actively adapted to hollow-back and rounded-backpositions. That provides for a changing pressure loading in respect ofthe intervertebral discs. As a consequence of that changing pressureloading, the advantage is enjoyed that the intervertebral disc isnourished as a consequence of its “sponge principle”.

In the case of the seat according to the invention, it has proven to bedesirable if the backrest in a steeply inclined setting is set curvedconvexly forwardly into an associated lordosis position and in ashallowly inclined position is set curved concavely rearwardly into anassociated kyphosis position. That provides that the respective user ofthe seat assumes a hollow-back configuration in the correspondingupright position of the seat and a rounded-back configuration in aflatter position. It will be appreciated that it is also possible toprovide for a kyphosis position in a steeply inclined position and alordosis position in a flatly inclined position.

In the case of the seat according to the invention the seat squab can bestationary, that is to say non-adjustable. It is however also possiblefor the seat squab to be displaceable in the longitudinal direction ofthe seat and for the backrest to be displaceable in respect of itsinclination and thus between lordosis and kyphosis settings, independence on the longitudinal seat squab setting. That provides anincrease level of seat comfort, in comparison with a seat according tothe invention with a seat squab which is not displaceable. In the caseof a seat of the last-mentioned kind, it has proven to be advantageousif the backrest, in a set-back position of the seat squab, is setsteeply inclined into a corresponding lordosis position and, in aset-forward position of the seat squab, the backrest is set in ashallowly inclined condition into a kyphosis position. That can takeeven better account of the anatomical aspects of seat users of differentsizes.

Likewise it is possible for the seat squab to be displaceable in respectof its inclination and for the backrest to be displaceable in respect ofits inclination and thus between lordosis and kyphosis positions, independence on the inclination of the seat squab. In a seat of thelast-mentioned kind in a shallow position of inclination of the seatsquab the backrest can be set in a steeply inclined condition into anassociated lordosis position and in a forwardly upwardly inclinedposition it can be set in a shallowly inclined condition into anassociated kyphosis position. This also makes it possible to takeaccount of the anatomical factors of various users of the seat.

A still more improved seat with enhanced seat comfort is afforded if theseat squab is displaceable in the longitudinal direction of the seat andsimultaneously in respect of its inclination and therewith the backrestis displaceable between corresponding lordosis and kyphosis positions.

In the case of the seat according to the invention the backrest can bedisplaceable statically between lordosis and kyphosis positions. Asalready stated above, that not only provides for an alternating pressureloading in the intervertebral disc, but it also provides for nutritionfor the intervertebral disc as a consequence of its “sponge principle”.It can be desirable if, in the seat according to the invention, thebackrest is displaceable dynamically between lordosis and kyphosispositions in order not only to provide a desired pressure relief effectfor the intervertebral disc as well as nutrition therefor, but also toprovide a massage effect. All that has a correspondingly positive effectin terms of seat comfort.

Further details, features and advantages are apparent from thedescription hereinafter of embodiments of the seat according to theinvention which are diagrammatically illustrated in the drawing inwhich:

FIG. 1 shows a first embodiment of the seat with a non-displaceable seatsquab and a backrest which is displaceable in terms of its inclination,

FIG. 2 is a diagrammatic side view similar to FIG. 1 of a seat with adisplaceable seat squab and a backrest which is displaceable independence on the displacement of the seat squab,

FIG. 3 is a diagrammatic side view of a seat with a rigid base framestructure and a seat squab which is displaceable with respect theretoand a backrest in a lordosis position,

FIG. 4 shows the seat of FIG. 3 in a kyphosis position,

FIG. 5 diagrammatically shows an embodiment of the seat illustrated inFIG. 1 with a stationary seat squab, with the backrest assuming alordosis position,

FIG. 6 shows the seat of FIG. 5, with the backrest assuming a kyphosisposition,

FIG. 7 diagrammatically shows a further embodiment of the seatcorresponding to the seat shown in FIG. 1 with a stationary seat squab,with the backrest assuming a lordosis position,

FIG. 8 shows the seat of FIG. 7, with the backrest assuming anintermediate position between the lordosis position shown in FIG. 7 anda kyphosis position as shown in FIG. 9,

FIG. 9 shows the seat illustrated in FIGS. 7 and 8, wherein the backrestassumes a kyphosis position,

FIG. 10 is a view similar to FIG. 5 of a seat, wherein the seat squab isadjustable in the longitudinal direction of the seat and in respect ofits inclination, and

FIG. 11 shows the seat illustrated in FIG. 10, with the backrestassuming a kyphosis position.

FIG. 1 is a diagrammatic side view of a seat 10 comprising a seat squab12 and a backrest 14. The backrest 14 is displaceable in terms of itsinclination, with respect to the seat squab 12. This is indicated by thearcuate arrow 16. The backrest 14 is identified by solid lines in asteep inclined setting and with thin broken lines in a shallow inclinedsetting, and identified by reference numeral 14′. In the steep inclinedposition, the front surface 18 of the backrest 14 is set convexlyoutwardly into a lordosis position. In the shallow inclined position thefront surface 18′ of the backrest 14 assumes a concavely rearwardlycurved kyphosis position.

The seat squab 12 of the seat 10 illustrated in FIG. 1 can be arrangedstationarily, that is to say non-displaceably. In another embodiment ofthe seat 10 however the seat squab 12 can also be displaceable with areciprocating movement in the longitudinal direction of the seat. Thatis indicated by the double-headed arrow 20 in FIG. 1. In this case thebackrest 14 can be displaceable in dependence on the linear setting ofthe seat squab 12 in the longitudinal direction of the seat orindependently of that longitudinal setting.

FIG. 2 shows an embodiment of the seat 10 in which the seat squab 12 isadjustable in the longitudinal direction of the seat and at the sametime in respect of its inclination. Displacement of the seat squab 12 inthe longitudinal direction of the seat is again indicated by thedouble-head arrow 20. The inclined setting of the seat squab 12 isindicated by the arcuate double-head arrow 22. In the case of the seatshown in FIG. 2 the seat squab 12 can be displaceable in thelongitudinal direction of the seat and in respect of inclinationindependently of each other or in dependence on each other.

In the position of the seat squab 12 which is shown in solid lines inFIG. 2 the backrest 14 assumes a steep inclined setting. In the positionof the seat squab which is identified by reference numeral 12′ andindicated by thin broken lines, being the position in which the seatsquab is set forwardly in the longitudinal direction of the seat andraised at the front in an inclined condition, the backrest which isidentified with thin broken lines and which bears reference numeral 14′assumes a shallow inclined position. In the steep inclined position ofthe backrest 14 the front surface 18 thereof is curved convexlyforwardly in order to assume a lordosis position. In the shallowinclined position the front surface 18′ of the backrest 14′ is curvedconcavely rearwardly and assumes a rounded-back position, that is to saya kyphosis position.

FIGS. 3 and 4 diagrammatically show an embodiment of the seat10—similarly to the seat 10 shown in FIG. 2—wherein a rigid base framestructure 24 of the seat 10 is combined with a seat squab 12 and abackrest 14 in such a way that, in the rearwardly displaced and slightlyinclined position of the seat squab 12 the backrest is inclined steeplyand assumes a forwardly convexly curved lordosis position (see FIG. 3).When the seat squab 12 is displaced forwardly and upwardly at the frontthe backrest 14 assumes a shallow inclined position and is set in arearwardly curved kyphosis position (see FIG. 4). For that purpose therigid base frame structure 24 has for example a backrest portion 26, aseat squab portion 28 and a connecting portion 30 which connects thebackrest portion 26 to the seat squab portion 28. The backrest 14 has abuttocks portion 34 which is adjacent to the seat squab 12 and which ispivotably connected thereto by means of a pivot 32, and a shoulderportion 38 which is pivotably connected to the buttocks portion 34 bymeans of a pivot 36.

In the lordosis position which is diagrammatically shown in FIG. 3, thepivot 32 between the seat squab 12 and the backrest 14 is in the regionof the connecting portion 30 of the rigid base frame structure 24 of theseat 10. In the kyphosis position of the backrest 14 diagrammaticallyshown in FIG. 4, the pivot 32 is in the transitional region 39 betweenthe seat squab portion 28 and the connecting portion 30 of the rigidbase frame structure 24 of the seat 10. By virtue of displacement of theseat squab 12 in the longitudinal direction of the seat the inclinationof the seat squab 12 and the backrest 14 is automatically reciprocatedbetween the lordosis position (see FIG. 3) and the kyphosis position(see FIG. 4). That can be effected statically, that is to say byso-to-speak one-off displacement as desired, or dynamically, that is tosay with a reciprocating motion.

FIGS. 5 and 6 show a further embodiment of the seat 10 in a lordosisposition (see FIG. 5) of the backrest 14 and in a kyphosis position (seeFIG. 6) of the backrest 14. In this case the seat squab 12 can be forexample stationary, that is to say immovable, similarly to theembodiment of FIG. 1. Linear guides 40 and 42 are combined with the seatsquab 12. A guide member 44 is linearly movably guided along the linearguide 40 and a guide member 46 is linearly movably guided along thelinear guide 42. The guide members 44 and 46 are provided on a frameportion 48 which extends with a seat portion 50 under the seat squab 12and which has a backrest portion 52. Two backrest parts 54 and 56 aremounted to the backrest portion 52 pivotably about associated pivot axes58 and 60. When the frame portion 48 is in the position diagrammaticallyshown in FIG. 5, the backrest parts 54 and 56 assume a position suchthat the backrest 14 indicated in broken line assumes with its frontsurface 18 a lordosis position. In comparison, in the position indicatedin FIG. 6, the backrest parts 54 and 56 assume a rearwardly angledposition so that the backrest 14′ indicated in broken lines, with itsfront surface 18′, assumes a rearwardly concavely curved kyphosisposition.

In order to pivot the backrest part 56 from the position indicated inFIG. 5 into the rearwardly pivoted position about the pivot axis 60 inthe rearward pivotal movement of the backrest 14 which is indicated bythe arcuate arrow 62, the backrest part 56 is connected in positivelylocking relationship to a slide element 64. The slide element 64 isdisposed in fixed relationship with the seat.

The seat 10 shown in FIGS. 5 and 6 therefore involves the function ofthe seat 10 indicated in FIG. 1, with an immovable seat squab 12. Itwill be appreciated that it is also possible for the seat 10 shown inFIGS. 5 and 6 to be designed with a movable seat squab 12, correspondingto the operating principle illustrated in FIG. 2.

FIGS. 7, 8 and 9 diagrammatically show still another embodiment of theseat 10 with a seat squab 12 and a backrest 14. The seat squab 12 hasportions 66, 68 and 80. The backrest 14 has portions 72 and 74. Theportions 66 and 68 are rigidly connected to each other by means of aconnecting element 76. The connecting element 76 is stationary.

The portions 68 and 70 of the seat squab 12 are rigidly connected toeach other by means of a connecting element 78. A leg element 80 alsoprojects rigidly away from the connecting element 78 and is pivotablyconnected to a second leg element 82 by means of a pivot axis 84. Theportions 72 and 74 of the backrest 14 are pivotably connected by meansof a connecting element 86. The second leg element projects pivotablyaway from the connecting element 86. A third leg element 88 alsoprojects away from the connecting element 86. The second leg element 82and the third leg element 88 are rigidly connected together at theconnecting element 86 and are pivotable about the connecting element 86.

A spring element 94 is stressed between the end 90, which is remote fromthe connecting element 78, of the portion 70 of the seat squab 12 andthe end 92, which is remote from the connecting element 86, of thebackrest portion 72.

The third leg element 28 is pivotably connected by means of a pivot axis96 to a pivot element 98 which is pivotably connected to the end 90 ofthe portion 70 of the seat squab 12.

In FIG. 7, the backrest 14 assumes a steep inclined position, with theportions 72 and 74 thereof assuming a forwardly directed lordosisposition. In comparison, FIG. 9 shows a shallowly rearwardly inclinedposition of the backrest 14 in which its portions 72 and 74, beingangled rearwardly, assume a kyphosis position. FIG. 8 shows anintermediate position of the backrest 14 between the lordosis positionshown in FIG. 7 and the kyphosis position indicated in FIG. 9.

FIGS. 10 and 11 show another embodiment of the seat 10 in which the seatsquab 12 is displaceable in the longitudinal direction of the seat andat the same time in respect of its inclination. In FIG. 10 the backrest14 assumes a lordosis position while in FIG. 11 the backrest 14 assumesa kyphosis position. That is clearly shown by the front surface 18 ofthe backrest 14, as is shown in broken line.

The seat squab 12 of the seat 10 rests with its underside 100 on rollers102 which project upwardly from the linear guide 40. Projectingdownwardly from the underside 100 of the seat squab 12 are guide members46 which are movable along the linear guide 42. The linear guides 40 and42 are arranged in mutually facing relationship.

Guided movably along the linear guide 40 is a guide member 44 which isprovided on the seat portion 50 of the frame part 48. The frame part 48also has a backrest portion 52. The backrest portion 52 is fixedlyconnected to a backrest part 54 of the backrest 14. The backrest 14 hasa second backrest part 56 which is pivotably connected to the backrestportion 52 by means of a pivot axis 60. The backrest part 56 is mountedwith its lower edge which is remote from the pivot axis 60, on a slideelement 64.

In FIG. 10 the seat squab 12 is in a position of being set back in thelongitudinal direction of the seat and shallow in terms of itsinclination. With the seat squab 12 in that position the backrest 14 orthe front surface 18 thereof assumes a lordosis position. In comparisontherewith FIG. 11 shows a setting of the seat 10 in which the seat squab12 is set forwardly in the longitudinal direction of the seat, while theseat squab 12 at the same time assumes a position of being inclinedupwardly at the front. With the seat squab 12 in that position thebackrest 14 or the front surface 18 thereof assumes a kyphosis position.

It will be appreciated that the invention is not limited to theembodiments illustrated or diagrammatically indicated in the drawingsbut any other design configurations can also be adopted.

What is claimed is:
 1. A seat comprising a displaceable seat squab (12)and a backrest which is displaceable in respect of its inclinationbetween a convex lordosis position and a concave kyphosis position independence on the seat squab setting and which is set in a steepinclined position in a convexly forwardly curved configuration into anassociated lordosis position and in a shallow inclined position in aconcavely rearwardly curved configuration into an kyphosis position,characterized in that the seat squab (12) is displaceable in thelongitudinal direction of the seat and that the backrest (14) isdisplaceable in dependence on the seat squab longitudinal setting inrespect of its inclination, wherein in a set-back position of the seatsquab (12) the backrest (14) is set steeply inclinedly into anassociated lordosis position and in a set-forward position of the seatsquab (12) the backrest (14) is set in a shallowly inclined positioninto a corresponding kyphosis position.
 2. A seat as set forth in claim1 characterized in that the backrest (14) is displaceable staticallybetween lordosis and kyphosis positions.
 3. A seat as set forth in claim1 characterized in that the backrest (14) is displaceable dynamicallybetween lordosis and kyphosis positions.